DESCRIPTION (Adapted from the Abstract): Staphylococcus aureus remains a leading cause of morbidity and mortality in both community and hospital settings. Multiple antibiotic resistant strains of s. aureus are common and we are one antibiotic away from returing to the pre antibiotic era, with its attendant high mortality rates, for infections with this bacterium. It is believed that fundamental studies of bacterial pathogenicity will provide the scientific platform for improved methods of disease control. Previous studies of the mechanisms of S. aureus pathogenicity have emphasized extracellular factors produced by the organism. The role of proteins produced in response to the stresses of the host environment in bacterial pathogenicity has been increasingly recognized of late. This study will examine the hypothesis that novel S. aureus stress-induced virulence factors and associated regulatory elements can be isolated on the basis of mRNA expression. The polymerase chain reaction based approach known as differential display will be used to detect differences in mRNA expression in response to stresses mimicking those of the host environment. These studies may result in the identification of novel targets for antimicrobial agents.